Method of making a sandwich material with internal undulations a

Details Method of making a sandwich material with internal undulations a Method of making a sandwich material with internal undulations a

1985-09-09

1988-08-23

Weston, Caleb

Adhesive bonding and miscellaneous chemical manufacture

Methods

Surface bonding and/or assembly therefor

156208, 156210, 156470, B32B 3112

Patent

active

047658550

DESCRIPTION:

BRIEF SUMMARY
The invention is primarily concerned with a new material based on paper, having a central core of corrugated paperboard and an external plastic protection to confer resistance to humidity.
The material of the invention is of the type comprising a central core made of corrugated paper sheets separated by intermediate paper sheets and coated on at least one side by a film of thermoplastic material.
For reasons which will be elaborated upon later, it is rather unusual to associate paper sheets with a sheet of thermoplastic material when developping new types of sandwich materials.
A first known thermoplastic material-paper sandwich is the protective sheet schematically represented in cross section in FIG. 1 of the drawings.
FIG. 1 shows a protective sheet (1) comprised of a supporting paper sheet (3) coated on one side (2) by a film of a thermoplastic material (4), such as polyethylene or polypropylene. This material is used for covering and packaging applications where the paper (1) needs to be protected from humidity. Quite obviously, a similar supporting sheet (3') as shown in FIG. 2 can be coated with a thermoplastic film on both sides (2' and 4').
A second type of thermoplastic material-paper sandwich (5) is schematically represented also in cross section in FIG. 3.
This material comprises a thermoplastic film (3") sandwiched between two sheets of paper 6 and 7. This film confers special mechanical properties to this material which is commonly referred to as "Paratene".
Further, a most widely used material based exclusively on paper called "corrugated paperboard" (9) is schematically represented in FIG. 4.
This material (9) comprises a central core (11) made of a sheet of paper shaped into a succession of corrugations (13). Both sides of the core are covered with a sheet of paper (17, 18).
The covering sheet (17) is bonded to the ridges (14) of the corrugations (13) on the first side of the paper (12) forming the core along the lines (19) where the ridges (14) of the corrugations (13) meet the sheet (17). The other covering sheet (18) is bonded to the core (11) on the second side of the paper (12) along the lines (20) where the ridges (15) meet the sheet (18).
The object of the invention is primarily a sandwich material where the core is made of a block of corrugated paperboard protected and covered on one or both sides by a plastic material.
In principle, the known manufacturing process for corrugated paperboard consisting of one flat sheet of protective paper bonded on a corrugated core first comprises the steps of producing a web of intermediate protective paper and feeding this web to a machine producing the corrugated paperboard. A web of core paper having the same width as the web of protective paper is fed to two serrated rolls for impressing transverse corrugations. The web of protective paper and the sheets of corrugated paper are fed at the same speed.
The ridges on the second side of the core paper are then coated with adhesive, and the core paper is fed to the part of the machine where the core paper is bonded to the protective paper. The two webs are fed with the side of the core coated with adhesive facing the inner side of the protective paper.
The web of protective paper is mainained facing the part of the machine where the bonding is effected by means of intermediate rollers. The corrugated paper is fed between one of the rollers and the protective paper. The second side of the corrugated paper is thereby pressed against the inner side of the protective web.
The adhesive used as a solution for bonding the web of protective paper to the ridges of the corrugated core is usually of a type polymerizing through an exothermic reaction. The adhesive preparations normally used are starch-based water solutions. When this is actually the case, the water opens the pores of the two webs. The bonding of these webs together requires a heat treatment which breaks the starch grains open. For this purpose, the machine comprises heating elements for increasing the temperature of the two paper webs when th

REFERENCES:
patent: Re29272 (1977-06-01), Hintz et al.
patent: 2102937 (1937-12-01), Bauer
patent: 3290205 (1966-12-01), Goldstein et al.
patent: 3307994 (1967-03-01), Scott

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